Conventional ventilation duct systems are composed of elongate straight parts and a large number of different connectors and end pieces, such as pipe bends, T-pieces, end outlets etc., which allows the ducts to be laid in forms deviating from the straight form.
To make it possible to mount a ventilation duct system to suit its purpose, a great variety of connectors must be available. For example, pipe bends must be manufactured to have different angles, e.g. up to 90.degree. in steps of 15.degree., which means that a very great number of variants must be manufactured in advance and stored, thus implying heavy capital expenditure for stock-keeping.
Moreover, the finished connectors are relatively bulky to store and transport, which also results in high costs.
An object of the invention is to provide a solution to these problems.